Thyroid Hormone Homeostasis in Levothyroxine-treated Patients: Findings From ELSA-Brasil

[helvella]

Thyroid Hormone Homeostasis in Levothyroxine-treated Patients: Findings From ELSA-Brasil

I’ve only just read some of this paper.

I think there are some important points:

I do not think they considered any possible conversion by the thyroid but only original production of T3.

I do not think they considered, even speculated, that if someone needs thyroid hormone, but still has a functioning thyroid, their thyroid capacity is likely to reduce over the years. Thus, to begin with, there will be a reduction in T3 creation (and conversion), after years that capacity might well reduce. This could be due to autoimmune destruction or simply reduction in thyroid size due to long-term levothyroxine treatment.

This might help to explain the number of people who are seemingly OK, sometimes for many years, but who then deteriorate markedly.

I recommend reading the Discussion which is very clear. The writing is unusually good for such papers. As if they actually want everyone to be able to read it and understand the message.

Thyroid Hormone Homeostasis in Levothyroxine-treated Patients: Findings From ELSA-Brasil.

Penna GC 1 , Bensenor IM 2 , Bianco AC 1 , Ettleson MD 1

Abstract 

Context

The effectiveness of levothyroxine (LT4) in restoring thyroid hormone (TH) homeostasis, particularly serum thyroxine (T4) and triiodothyronine (T3) levels, remains debatable.

Objective

This work aimed to assess TH homeostasis in LT4-treated individuals using data from the Longitudinal Study of Adult Health in Brazil (ELSA-Brasil) study.

Methods

The ELSA-Brasil study follows 15 105 adult Brazilians (aged 35-74 years) over 8.2 years (2008-2019) with 3 observation points assessing health parameters including serum thyrotropin (TSH), free T4 (FT4), and free T3 (FT3) levels. We analyzed 186 participants that initiated treatment with LT4 during the study, and 243 individuals continuously treated with LT4 therapy.

Results

Initiation of therapy with LT4 resulted in an 11% to 19% decrease in TSH, an approximately 19% increase in FT4, and a 7% reduction in FT3 serum levels (FT3 dropped >10% in ∼40% of the LT4-treated patients). This was associated with an increase in triglyceride levels and utilization of hypolipidemic and antidiabetic medications. Participants continuously treated with LT4 exhibited a stable elevation in serum FT4 and a reduction in serum FT3 and TSH levels. While 115 participants (47.3%) had at least 1 serum FT4 levels above the control reference range (>1.52 ng/dL), 38 participants (15.6%) had at least 1 serum FT3 below the reference range (<0.23 ng/dL).

Conclusion

The present results challenge the dogma that treatment with LT4 for hypothyroidism restores TH homeostasis in all patients. A substantial number of LT4-treated patients exhibit repeated FT4 and FT3 levels outside the normal reference range, despite normal TSH levels. Further studies are needed to define the clinical implications of these findings.

Open access on journal site and within EuropePMC:

europepmc.org/article/MED/3...

doi.org/10.1210/clinem/dgae139

academic.oup.com/jcem/artic...

[jgelliss]

Helvella this is a bit interesting to me🤔.If I'm not mistaking Helvella I think you dose with T4 only. Is this a scare tactic? Is this your belief too? Many are on T4 only. Is this something to worry about now too? As if we didn't have what to worry about?

[helvella in reply to jgelliss]

Yes - I take T4 only.

But I am quite comfortable with the idea that T3 really is needed by many, most, even all, of us.

We end up with relatively high FT4, and relatively low FT3. Which might be close enough to being OK for many. However, it clearly isn't good enough for a lot of us.

I'd very much like the opportunity to take minuscule doses of T3 in a properly managed form to achieve my current FT3 levels - or possibly the tiniest bit higher - but marginally reduce my FT4. And I really mean starting with one or two micrograms and very slowly increasing depending on experience.

Maybe the hoped-for polyzincliothyronine? Or liothyronine sulphate?

For myself, it is probably never going to be feasible. Not worth going out on a limb and trying to do it on my own because I doubt it would make that much difference. I do seem to have acceptable FT3 levels and no obvious hypothyroid symptoms. (I'd like to know if my atrial fibrillation might improve?) And It is unlikely to become readily available in the foreseeable future.

[jgelliss in reply to helvella]

Helvella I totally agree with you. Your talking about someone like myself. I do well with high FT4 with a lower FT3. The T3 is very Helpful with the palpitations that I experienced on T4 only. Thank You for your kind response and your Great and Helpful Posts.

[eeng]

Very interesting

[tattybogle]

interesting ... have added it to my collection of evidence that t3 is lower on levo : healthunlocked.com/thyroidu.... tsh-is-just-the-opinion-of-your-pituitary-about-your-dose-but-your-pituitarys-opinion-is-a-bit-warped-once-you-take-thyroid-hormone.

hi ho , hi ho , it's off to work i go .... see you later folks

[Calceolaria]

Thank you! More to mull over. I apologise in advance for this but - T4 is counterproductive to the health of the thyroid gland? But necessary for the health of every other cell in the body? Where/what is the disconnect? OK, so it’s in the conversion to T3 but - I don’t know what I’m reaching for here….! There still feels to be a disconnect.